Device and procedure for pericardial patch transcatheter atrial septal defect closure

ABSTRACT

A device for closure of an atrial septal defect (ASD) by deploying a pericardial patch includes a head including a distal jaw and a proximal jaw, and a distal disc attached to the distal jaw and a proximal disc attached to the proximal jaw. Each of the distal jaw and the proximal jaw includes at least one arm which closes when the distal disc moves forward and the proximal disc moves backward. Based on an engagement status of a distal engagement portion located on the at least one arm of the distal jaw with a proximal engagement portion located on the at least one arm of the proximal jaw, the pericardial patch deploys to close the ASD.

The present application is a Continuation Application of U.S.application Ser. No. 15/338,419, filed on Oct. 30, 2016, which is aContinuation-In-Part application of U.S. application Ser. No.14/947,598, filed on Nov. 20, 2015, now U.S. Pat. No. 9,480,469, whichis a Continuation Application of U.S. application Ser. No. 13/835,587,filed on Mar. 15, 2013, now U.S. Pat. No. 9,192,365, which is aDivisional Application of U.S. application Ser. No. 12/654,978, filed onJan. 12, 2010, now U.S. Pat. No. 8,398,658, which benefits a priorityfrom U.S. Provisional Patent Application No. 61/154,388, filed on Feb.21, 2009, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method for providing a minimallyinvasive closure of atrial septal defect without cardiopulmonary bypassand, in particular, a device and a method for minimally invasive closureof atrial septal defect via a right minithoracotomy to deploy apericardial patch under a transesophageal echocardiography guidance.

Description of the Related Art

There are currently two methods for the closure of atrial septal defect(ASD), conventional or minimally invasive surgical method andpercutaneous device transcatheter closure. The former requirescardiopulmonary bypass (CPB), and the latter, which entails thedeployment of a sizable device in the heart, is hampered by the defectsize and circumferential margins adjacent to the superior and inferiorvenae cavae, pulmonary vein, mitral valve, and aortic sinus.

Recently, robotically assisted surgical systems have enhanced theprecision of minimally invasive cardiac surgery. These costlyprocedures, however, still require the CPB. CPB is widely recognized ashaving a number of adverse effects, including generation of microemboliand an inflammatory response associated with increased cytokineproduction and complement activation, begetting neurological dysfunctionin adults and neurodevelopmental dysfunction especially in children.

In addition, recently cosmetic sequelae following cardiac surgery hasrendered minimal access approaches with equivalent results and a nearlyinvisible scar is more favorable.

SUMMARY OF THE INVENTION

In view of the foregoing and other exemplary problems, disadvantages,and drawbacks of the aforementioned devices and methods, it is anexemplary purpose of the present invention to provide a device and amethod for minimally invasive closure of atrial septal defect withoutcardiopulmonary bypass.

The present invention includes a surgical device and method for closureatrial septal defect with minimally invasive approach. The deviceincludes a head portion which is movable and includes a distal jawplaced distal relative to a person holding the surgical device, a guiderod which drives the distal jaw, and a plurality of first suture-guidechannels attached to the distal jaw, and a body portion which isstationary and includes a cylindrical base, a proximal jaw attached tothe cylindrical base, and a plurality of second suture-guide channelsattached to the proximal jaw.

The guide rod drives the distal jaw to pass a pericardium patch througha patient's ASD while the proximal end remains extracorporeal. The firstsuture-guide channels and the second suture-guide channels guide asuture thread to suture the pericardium patch onto an ASD rim.

The head portion may include four first suture-guide channels, and thebody portion may include four second suture-guide channels.

Further, each of the first suture-guide channels includes an arm whichconnects a center portion of each of the first suture-guide channels tothe distal jaw. Each of the first suture-guide channels may be spacedapart from an adjacent one of the first suture-guide channels such thatthe arm of the each of the first suture-guide channels is oriented at 90degrees with respect to an arm of the adjacent one of the firstsuture-guide channels.

Also, each of the second suture-guide channels includes an arm whichconnects a center portion of each of the second suture-guide channels tothe proximal jaw. Each of the second suture-guide channels may be spacedapart from an adjacent one of the second suture-guide channels such thatthe arm of the each of the second suture-guide channels is oriented at90 degrees with respect to an arm of the adjacent one of the secondsuture-guide channels. The first suture-guide channels may be orientedat 90 degrees to the second suture-guide channels such that the firstsuture-guide channels couple with the second suture-guide channels toform a circle.

In the surgical device, the first suture-guide channels are attached toa plurality of first arms, each of the first arms connects a centerportion of each of the first suture-guide channels to the distal jaw.The first arms may be oriented at 0, 90, 180, and 270 degrees withrespect to a center of the guide rod.

Further, the second suture-guide channels are attached to a plurality ofsecond arms, each of the second arms connects a center portion of eachof the second suture-guide channels to the proximal jaw. The second armsmay be oriented at 45, 135, 225, and 315 degrees with respect to thecenter of the guide rod.

In the surgical device, the pericardial patch is connected to a suctiondevice via a flexible pipe. Also, a threading thread attaches thepericardial patch to the distal jaw, in which ends of the threadingthread are extracorporeal.

Further, a lever drives the distal jaw away from the proximal jaw suchthat the distal jaw and the proximal jaw are spaced on different sidesof an ASD hole. After the suture thread sutures the pericardium patch,the lever pulls the distal jaw backward toward the proximal jaw suchthat the first suture-guide channels couple with the second suture-guidechannels to form a circle.

The lever may include a wire and a spring or a crown wheel and a pinion.The level drives the distal jaw by pulling the wire.

In the surgical device, the first suture-guide channels and the secondsuture-guide channels guide a needle that carries the suture thread tosuture the pericardium patch onto the ASD rim. The needle includes along malleable needle, and passes the suture thread through a spacebetween the guide rod and an internal section of the cylindrical base.The pericardium patch may be glued to the distal jaw.

Another aspect of the present invention includes a method of providing asurgical device for closure of atrial septal defect with minimallyinvasive approach.

The method includes drawing a pericardial patch over a distal jaw of thesurgical device, while keeping a first suture-guide channels attached tothe distal jaw and a second suture-guide channels attached to a proximaljaw of the surgical device closed, inserting the surgical device througha hole incised in an intercostal space of a patient and drawing thesurgical device toward the ASD, while keeping the proximal end of thesurgical device extracorporeal, manipulating forward a guide rod of thesurgical device to drive the distal jaw to negotiate the distal jawthrough the ASD, opening the first suture-guide channels and the secondsuture-guide channels to position the first suture-guide channels andthe second suture-guide channels around the ASD, withdrawing the distaljaw such that the distal jaw latches onto the proximal jaw, pulling backthe pericardial patch in conjunction with an ASD rim to secure thepericardial patch and the ASD rim between the first suture-guidechannels and the second suture-guide channels, employing a longmalleable needle extracorporeally to pass a suture thread into a spacebetween the guide rod and an internal part of a cylindrical base, whichsupports a body portion of the surgical device, to suture thepericardial patch onto the ASD rim through the first suture-guidechannels and the second suture-guide channels, re-steering forward thedistal jaw to release the pericardial patch and to suture thepericardial patch onto the ASD rim, shutting the first suture-guidechannels and the second suture-guide channels into respective originalpositions on the distal jaw and the proximal jaw, withdrawing the distaljaw from the ASD and lodging the distal jaw upon the proximal jaw,removing the surgical device from a body of the patient, and orienting aplurality of knots extracorporeally toward the ASD to complement thesuture of the pericardial patch.

The first suture-guide channels may be attached to a plurality of firstarms, each of the first arms connects a center portion of each of thefirst suture-guide channels to the distal jaw. The first arms may beoriented at 0, 90, 180, and 270 degrees with respect to a center of theguide rod. The second suture-guide channels may be attached to aplurality of second arms. Each of the second arms connects a centerportion of each of the second suture-guide channels to the proximal jaw.The second arms may be oriented at 45, 135, 225, and 315 degrees withrespect to the center of the guide rod.

In the method, after the suture thread sutures the pericardium patch, alever pulls the distal jaw backward toward the proximal jaw such thatthe first suture-guide channels couple with the second suture-guidechannels to form a circle.

Further, each of the first suture-guide channels includes an arm whichconnects a center portion of each of the first suture-guide channels tothe distal jaw. Each of the first suture-guide channels is spaced apartfrom an adjacent one of the first suture-guide channels such that thearm of the each of the first suture-guide channels may be oriented at 90degrees with respect to an arm of the adjacent one of the firstsuture-guide channels. Each of the second suture-guide channelscomprises an arm which connects a center portion of each of the secondsuture-guide channels to the proximal jaw.

Each of the second suture-guide channels is spaced apart from anadjacent one of the second suture-guide channels such that the arm ofthe each of the second suture-guide channels may be oriented at 90degrees with respect to an arm of the adjacent one of the secondsuture-guide channels. The first suture-guide channels may be orientedat 90 degrees to the second suture-guide channels such that the firstsuture-guide channels couple with the second suture-guide channels toform a circle.

With its unique and novel features, the present invention provides adevice and a method for minimally invasive approach for the closure ofall forms and sizes of secundum ASD which obviates the need for CPB,radiation, and deployment of an expensive bulky device in the heart.This procedure is carried out via a right minithoracotomy to deploy apericardial patch under transesophageal echocardiography guidance. Themethod of the present invention does not require additional work for theclosure of more than one defect with aneurismal rims or defects withdeficient margins. Further, it offers an added element of safetycompared with the transcutaneous route, because the procedure isperformed in an operating room with CPB facilities available for anyexigencies. This approach also minimizes the risk of atrioventricularvalve distortion and obstruction of the superior and inferior venaecavae or coronary sinus.

Other advantages of this technique are reduced associated pain, bettercosmetic results, shorter recovery time, and fewer complications.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other exemplary purposes, aspects and advantages willbe better understood from the following detailed description of theexemplary embodiments of the invention with reference to the drawings,in which:

FIG. 1 illustrates an exemplary device for minimally invasive closure ofatrial septal defect, in accordance with an exemplary aspect of thepresent invention;

FIG. 2a illustrates a view of the distal jaw while the suture-guidechannels remain shut, before drawing a pericardium patch over the devicefor minimally invasive closure of atrial septal defect, in accordancewith an exemplary aspect of the present invention;

FIG. 2b illustrates a view of the distal jaw while the suture-guidechannels remain shut, after drawing a pericardium patch over the devicefor minimally invasive closure of atrial septal defect, in accordancewith an exemplary aspect of the present invention;

FIG. 3 illustrates a cross section view of heart, the ASD, and thedistal jaw of the device while it advanced toward the ASD, in accordancewith an exemplary aspect of the present invention;

FIG. 4 illustrates a cross sectional view of the ASD while thesuture-guide channels are opened and positioned around, in accordancewith an exemplary aspect of the present invention;

FIG. 5a illustrates a view of the device when the distal jaw iswithdrawn and pericardium patch in conjunction with the ASD rim isfirmly secured between the suture-guide channels, in accordance with anexemplary aspect of the present invention;

FIG. 5b illustrates a view of the device when the distal jaw iswithdrawn and latches onto the proximal jaw, in accordance with anexemplary aspect of the present invention;

FIG. 6 illustrates a view of the device while the distal jaw isre-steered forward to releases the pericardium patch for snugly suturingonto the ASD rim, in accordance with an exemplary aspect of the presentinvention;

FIG. 7 illustrates cross section view of the heart after closure of theASD, in accordance with an exemplary aspect of the present invention;

FIG. 8 illustrates an exemplary device for transcatheteral closure ofatrial septal defect, in accordance with an exemplary aspect of thepresent invention;

FIG. 9 illustrates the head portion of device for transcatheteralclosure of atrial septal defect, in accordance with an exemplary aspectof the present invention;

FIG. 10a illustrates a view of the head while the arms of both distaland proximal jaws remain shut, before drawing a pericardium patch overthe device for transcatheteral closure of atrial septal defect, inaccordance with an exemplary aspect of the present invention;

FIG. 10b illustrates a view of the head while the arms of both distaland proximal jaws remain shut, after drawing a pericardium patch overthe device for transcatheteral closure of atrial septal defect, inaccordance with an exemplary aspect of the present invention;

FIG. 11 illustrates a cross section view of heart, the ASD, and thedistal jaw of the device while it advanced toward the ASD, in accordancewith an exemplary aspect of the present invention;

FIG. 12 illustrates a cross sectional view of the ASD while the bothjaws are opened and positioned around, in accordance with an exemplaryaspect of the present invention;

FIG. 13 illustrates a view of the device when the distal jaw iswithdrawn and pericardium patch in conjunction with the ASD rim isfirmly secured between distal and proximal jaws and pins lached into thesockets, in accordance with an exemplary aspect of the presentinvention; and

FIG. 14 illustrates a view of the device while the distal jaw isre-steered forward to releases the pericardium patch for snugly fixingonto the ASD rim, in accordance with an exemplary aspect of the presentinvention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

Referring now to the drawings, FIG. 1 illustrates an exemplary aspect ofthe present invention. Specifically, FIG. 1 illustrates an exemplarydevice 100 for minimally invasive closure of atrial septal defectwithout cardiopulmonary bypass, in accordance with an exemplary aspectof the present invention.

As shown in FIG. 1, the device includes two main parts, a head, which ismoveable and includes of a guide rod (b), distal jaw, relative to theperson holding the device (a), and 4 suture-guide channels (c), and abody, which is stationary and includes a cylindrical base (d), aproximal jaw (e), relative to the person who holds the device, and 4suture-guide channels (t). The 8 suture-guide channels (c) and (f),oriented at 90 degrees relative to one another and mounted upon thedistal jaw (a) and proximal jaw (e), form a circle, with the channels atthe distal jaw (a) being at 0, 90, 180, and 270 degrees and the channelsat the proximal jaw (e) being at 45, 135, 225, and 315 degrees such thatthe channels can slide open and shut radially.

A 3-cm incision is arranged in the right fourth midaxillary intercostalspace. The lateral mini thoracotomy exposes the pericardium, which isopened and sutured with five 2-0 stay sutures to suspend the heart.Right atriotomy follows the placement of two parallel 4-0 polypropylenepurse string sutures, approximately 10 mm in diameter. The patient isthen administered about 1.0 mg/kg of heparin, and the activated clottingtime is confirmed to be greater than 250 s.

A pericardium patch, with the desired size for the closure of ASD, iscut and drawn over the distal jaw (a) while the suture-guide channels(c) and (f) remain shut, as shown in the exemplary FIGS. 2a and 2 b.

The device is thereafter inserted through the hole incised in thepatient's intercostal space and advanced toward the ASD, while theproximal end of the device body, relative to the person using thedevice, remains extracorporeal, as illustrated in the exemplary FIG. 3.

The guide rod (b) is manipulated to drive the distal jaw (a) forward andnegotiate it through the ASD.

As shown in the exemplary FIG. 4, in this exemplary aspect, thesuture-guide channels (c) and (f) are subsequently opened and positionedaround the ASD.

The distal jaw (a) is withdrawn so that it latches onto the proximal jaw(e), to pull back the pericardium patch in conjunction with the ASD rimand firmly secure them between the suture-guide channels (c) and (f), asdepicted in the exemplary FIGS. 5a and 5 b.

A long malleable needle is employed extracorporeally to pass a suturethread into the space between the guide rod (b) and the internal part ofthe cylindrical base (d) and to suture the pericardium patch onto theASD rim through the suture-guide channels (c) and (f).

The distal jaw (a) is re-steered forward so that it releases thepericardium patch, which is snugly sutured onto the ASD rim, asillustrated in the exemplary FIG. 6.

The suture-guide channels (c) and (f) are shut and retracted to theirrespective original positions on the jaws. The distal jaw (a) isafterward withdrawn through the ASD and is lodged upon the proximal jaw(e), as shown in the exemplary FIG. 7.

Then, the device is extracted from the patient's body. Finally, adesired number of knots are arranged extracorporeally and the knots arethen oriented toward the ASD so as to complement the suturing of thepericardium patch. The chest is closed as per normal with no drainagetube placement.

Another exemplary aspect of the present invention is directed to amethod of providing a surgical device for closure of ASD with minimallyinvasive approach.

The method includes drawing a pericardial patch over a distal jaw of thesurgical device, while keeping a first suture-guide channels attached tosaid distal jaw and a second suture-guide channels attached to aproximal jaw of the surgical device closed, inserting the surgicaldevice through a hole incised in an intercostal space of a patient anddrawing the surgical device toward the ASD, while keeping the proximaljaw of the surgical device extracorporeal, manipulating forward a guiderod of the surgical device to drive the distal jaw to negotiate thedistal jaw through the ASD, opening the first suture-guide channels andthe second suture-guide channels to position the first suture-guidechannels and the second suture-guide channels around the ASD,withdrawing the distal jaw such that the distal jaw latches onto theproximal jaw, pulling back the pericardial patch in conjunction with anASD rim to secure the pericardial patch and the ASD rim between thefirst suture-guide channels and the second suture-guide channels,employing a malleable needle extracorporeally to pass a suture threadinto a space between the guide rod and an internal part of a cylindricalbase, which supports a body portion of the surgical device, to suturethe pericardial patch onto the ASD rim through the first suture-guidechannels and the second suture-guide channels, re-steering forward thedistal jaw to release the pericardial patch and to suture thepericardial patch onto the ASD rim, shutting the first suture-guidechannels and the second suture-guide channels into respective originalpositions on the distal jaw and the proximal jaw, withdrawing the distaljaw from the ASD and lodging the distal jaw upon the proximal jaw,removing the surgical device from a body of the patient, and orienting aplurality of knots extracorporeally toward the ASD to complement saidsuture of the pericardial patch.

The method may further include driving the distal jaw away from theproximal jaw by a lever such that the distal jaw and the proximal jaware spaced on different sides of an ASD hole, and after the suturethread sutures the pericardium patch, pulling the distal jaw backwardtoward the proximal jaw by the lever such that the first suture-guidechannels couple with the second suture-guide channels to form a circle.

FIG. 8 illustrates an exemplary aspect of the second device of thepresent invention. Specifically, FIG. 8 illustrates an exemplary devicefor transcathetral closure of atrial septal defect withoutcardiopulmonary bypass, in accordance with an exemplary aspect of thepresent invention.

As shown in FIG. 8, the device consists of two parts: a guide (g) and ahead (j). The guide is comprised of guide knobs (h), which move theguide levers forward and backward via a rod (i) and control thedifferent components of the head (j). The head itself comprises variousparts, depicted in FIG. 9. The head has two main parts: the distal jaw(k) (the jaw which is distal relative to the operator) and the proximaljaw (l). Each jaw has 8 arms (m), which close through the pull of thestrings (p) when the distal disc (n) moves forward and the proximal disc(o) moves backward or vice versa open through the direct pressure on thearms (m) when the distal disc (n) moves backward and the proximal disc(o) moves forward. When the arms (m) on both jaws (k & l) are completelyopen, the pins (q) and the sockets (r) are aligned. The pins (q) and thesockets (r) can be completely engaged with the simultaneous forwardpressure of the entire proximal jaw (l) and the backward pressure of theentire distal jaw (k). When the distal jaw (k) moves forward and theproximal jaw (l) moves backwards simultaneously, the pins (q) and thesockets (r) are released.

A pericardium patch, with the desired size for the closure of the ASD,is cut and drawn over the distal jaw (k) while the arms (m) remain shutand both jaws (k & l) are in the rod (i) (FIG. 10a and FIG. 10b ). Therod (i) is entered into the jugular or femoral vein and is moved to theproximity of the ASD. Thereafter, the distal jaw (k) is steered forwardby tweaking the guide knobs (h) while the proximal jaw (l) of the deviceremains extracorporeal (FIG. 11). The arms (m) on both jaws (k & l) aresubsequently opened by moving the distal disc (n) and the proximal disc(o) with a tweak of the guide knobs (h) and are positioned around theASD (FIG. 12). Next, the distal jaw (k) is withdrawn so that it latchesonto the proximal jaw (l), pulling back the pericardium patch inconjunction with the ASD rim and firmly securing them between the arms(m). The pins (q) latch into the sockets (r) and secure the pericardiumaround the ASD (FIG. 13). The distal jaw (k) and the proximal jaw (l)are re-steered forward and backward so that they can release the pins(q), the sockets (r), and the pericardium patch—with the lattereventually becoming snugly fixed onto the ASD rim (FIG. 14). The distaljaw (k) is afterward withdrawn through the ASD and is lodged upon theproximal jaw (l). The head (j) is withdrawn into the rod (i) andextracted from the patient's body. The pins (q) and the sockets (r) aremade of material compatible with the body and after a while, the emptyspace between them and they themselves will be covered with the propertissue.

The device and method of the present invention enables that theminimally invasive closure of atrial septal defect procedure beperformed in the operating room with CPB facilities available for anyexigencies. This approach also minimizes the risk of atrioventricularvalve distortion and obstruction of the superior and inferior venaecavae or coronary sinus.

While the invention has been described in terms of one or moreembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims. Specifically, one of ordinary skill in the art willunderstand that the drawings herein are meant to be illustrative, andthe design of the inventive assembly is not limited to that disclosedherein but may be modified within the spirit and scope of the presentinvention.

Further, Applicants' intent is to encompass the equivalents of all claimelements, and no amendment to any claim the present application shouldbe construed as a disclaimer of any interest in or right to anequivalent of any element or feature of the amended claim.

What is claimed is:
 1. A device for closure of an atrial septal defect(ASD) by deploying a pericardial patch, said device comprising: a headcomprising a distal jaw and a proximal jaw; and a distal disc attachedto the distal jaw and a proximal disc attached to the proximal jaw,wherein each of the distal jaw and the proximal jaw includes at leastone arm which closes when the distal disc moves forward and the proximaldisc moves backward, and wherein, based on an engagement status of adistal engagement portion, located on the at least one arm of the distaljaw, with a proximal engagement portion located on the at least one armof the proximal jaw, the pericardial patch deploys to close the ASD. 2.The device of claim 1, wherein the distal engagement portion comprises apin and the proximal engagement portion comprises a socket.
 3. Thedevice of claim 2, wherein, when the at least one arm of the distal jawand the at least one arm of the proximal jaw are completely open, thepin and the socket engage with each other.
 4. The device of claim 3,wherein, when the distal jaw moves forward and the proximal jaw movesbackwards, the pin disengage from the socket.
 5. The device of claim 1,further comprising a guide that comprises guide knobs which move guidelevers of the guide forward and backward via a rod to control the head.6. The device of claim 1, wherein, when the distal disc moves forwardand the proximal disc moves backward, the at least one arm of the distaljaw and the at least one arm of the proximal jaw close.
 7. The device ofclaim 6, wherein, when the distal disc moves backward and the proximaldisc moves forward, the at least one arm of the distal jaw and the atleast one arm of the proximal jaw open.
 8. The device of claim 1,wherein, when the at least one arm of the distal jaw and the at leastone arm of the proximal jaw are completely open, the distal engagementportion and the proximal engagement portion engage with each other. 9.The device of claim 8, wherein, when the distal jaw moves forward andthe proximal jaw moves backwards, the distal engagement portiondisengages from the proximal engagement portion.
 10. The device of claim1, wherein, when the at least one arm of the distal jaw and the at leastone arm of the proximal jaw are completely open, the distal engagementportion and the proximal engagement portion engage with each other witha forward pressure of the proximal jaw and a backward pressure of thedistal jaw.
 11. The device of claim 10, wherein, when the distal jawmoves forward and the proximal jaw moves backwards, the distalengagement portion disengages from the proximal engagement portion. 12.The device of claim 1, wherein the pericardium patch is configured todrawn over the distal jaw while the at least one arm of the distal jawand the at least one arm of the proximal jaw are in a rod.
 13. Thedevice of claim 1, further comprising a guide that comprises guideknobs, wherein, when the guide knobs are actuated, the at least one armof the distal jaw and the at least one arm of the proximal jaw open bymoving the distal disc and the proximal disc to deploy the pericardialpatch configured to close the ASD.
 14. The device of claim 1, furthercomprising: strings connecting the at least one arm of the distal jaw tothe distal disc and further connecting the at least one arm of theproximal jaw to the proximal jaw.
 15. The device of claim 14, wherein,when the distal disc moves forward and the proximal disc moves backward,the distal jaw pulls the strings to close the at least one arm of thedistal jaw, and the proximal disc pulls the strings to close the atleast one arm of the proximal jaw.
 16. The device of claim 15, wherein,when the distal disc moves backward and the proximal disc moves forward,the distal jaw releases the strings to open the at least one arm of thedistal jaw, and the proximal disc releases the strings to open the atleast one arm of the proximal jaw.